1. Field of the Invention
The present invention relates to an apparatus for adjusting a position of a zoom lens barrel in which the position of a cam ring can be checked.
2. Description of Related Art
For example, in a known zoom lens barrel having a cam ring which is rotated to effect the zooming, the focal length during zooming is detected by a zoom code plate provided on a stationary ring of the zoom lens, together with zoom brushes which come into slide contact with the zoom code plate in accordance with the rotation of the cam ring, thus producing electric signals corresponding to the focal length.
The zoom code plate is provided with a predetermined pattern of contacts (contact pattern). Upon zooming, the zoom brushes are rotated together with the cam ring to come into slide contact with the zoom code plate, so that digital signals corresponding to the focal length can be sent to a drive control circuit of the camera. Consequently, data (e.g., open F number) necessary to control the camera is selected from each of a plurality of data tables of variable information, and input to the drive control circuit of the camera body.
Consequently, in the known zoom lens barrel as mentioned above, it is absolutely necessary to accurately place the zoom code plate and the zoom brushes at respective predetermined positions (reference positions). Otherwise, it is impossible to determine the angular position of the cam ring relative to the stationary ring of the zoom lens, thus resulting in a failure to detect a correct focal length during zooming.
However, in a conventional zoom lens barrel, the zoom code plate is circumferentially secured to the outer peripheral surface of the stationary ring, and the zoom brushes secured to the cam ring are rotated on the zoom code plate in the circumferential direction of the stationary ring. Consequently, it is very difficult to establish an accurate and optimal relative position of the zoom code plate and the zoom brushes by a fine adjustment, for example, upon assembling.